Alloys assistant to salt baths



United States Patent i ALLOYS ASSISTANT 'ro SALT BATHS Peter R. Marsh, Montclair, N. L, assignor to Driver- Harris Company, Harrison, N. J., a corporation of New Jersey No Drawing. Application March 13, 1956 Serial No. 571,142

Claims. (Cl. 75128) This invention relates to alloys, and more particularly to an alloy that is particularly useful in the manufacture of salt pots.

Salt pots, containers for neutral salt baths used in certain metal-treating processes, have been made of a nickel-chromium-iron alloy consisting of substantially 35% nickel, chromium, and balance essentially iron. The life of pots made of such alloys is short, and the pots frequently develop porosity in less than 24 hours. In United States Letters Patent No. 2,451,547, granted October 19, 1948, Howard M. German discloses an alloy in which substantially 2% of columbium is added to the 35-l5 nickel-chromium alloy. Such an alloy has been found to be a useful material for the manufacture of salt pots and its use increases their life toabout 10.0 hours.

I have found that the addition of very small amounts of nitrogen and selenium to an alloy of nickel, chromium and iron containing about 2% columbium greatly increases the life when such alloy is used in the manufacture of neutral salt pots. Such pots may be used for periods of 600 to 800 hours before porosity develops.

As stated the additions have been made to alloys of the 35-15 type, that is, 35 parts nickel, 15 parts chromium and balance iron. These proportions may, of course, vary within certain limits. The nickel content may vary from 32% to 38%, the chromium from 14% to with the balance essentially iron. The various addition elements, carbon, deoxidizers, nitrogen and selenium are added at the expense of the iron content.

The alloy may contain up to 1.5% carbon, from 1% to 2% manganese, from 1% to 2%, preferably more than 1.5 silicon, from 1% to 3% columbium and from 0.1% to 1.5% copper. Nitrogen and selenium are added to the melt in amounts that will leave measurable quantities of these elements in the final alloys. The nitrogen content is preferably between 0.1% and 0.15% but it may vary from 0.05% to 0.2%. The selenium is present in the final alloy in small proportions, less than 0.1%, generally about 0.05 Good results have been obtained from alloys containing as little as 0.01% selenium.

The alloys of the present invention may be prepared in the usual way for producing chromium-nickel-iron alloys. The addition elements are added, preferably during the latter part of the melting period. Columbium may be added'as the pure metal or as the less expensive ferrocolumbium. Nitrogen and selenium are preferably added in the form of nitrogen bearing ferro-chrome, and selenium in the form of ferro-selenium.

2,864,694 Patented pe 1s, 1.95

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. 2 a Analysis of typical heats of alloys ance with the invention are:

Throughout the specification and claims the expression balance iron means that, except for the elements enumerated and iron, the alloy is substantially free of other elements. It does not, however, exclude the presence of small amounts of other elements which do not affect the above described functions of columbium, nitrogen and selenium. Thus, in the specific examples given, the presence of manganese and silicon will be noted and other elements employed as deoxidizers in the melt, and generally used in slight excess, may likewise be present in substantially the same quantities.

The columbium contents cited throughout the specification may include residual amounts of tantalum, generally not greater than 0.5 percent. Commercial columbium and ferro-columbium contain small amounts of tantalum,

I claim:

1. An alloy consisting essentially of 32% to 38% nickel, 14% to 20% chromium, up to 1.5% carbon, 1% to 2% manganese, 1% to 2% silicon, 1% to 3% columbium, 0.05 to 0.2% nitrogen, .04% to 0.1% selenium, balance essentially iron.

2. An alloy consisting essentially of substantially 35% nickel, substantially 15% chromium, up to 1.5 carbon, 1% to 2% manganese, 1% to 2% silicon, 1% to 3% columbium, 0.05% to 0.2% nitrogen, .04% to 0.1% selenium, balance essentially iron.

3. An alloy consisting essentially of 32% to 38% nickel, 14% to 20% chromium, up to 1.5 carbon, 1% to 2% manganese, substantially 1.5% silicon, substantially 2% columbium, 0.1% to 0.15% nitrogen, substantially 0.05% selenium, balance essentially iron.

4. An alloy consisting essentially of substantially 35% nickel, substantially 15% chromium, up to 1.5% carbon, 1% to 2% manganese, substantially 1.5% silicon, substantially 2% columbium, 0.1% to 0.15% nitrogen, substantially 0.05 selenium, balance essentially iron.

5. An alloy consisting essentially of 32% to 38% nickel, 14% to 20% chromium, substantially 0.75% carbon, substantially 1.20% silicon, substantially 2.15% columbium, substantially .13% nitrogen, substantially 0.04% selenium, balance essentially iron.

6. An alloy consisting essentially of substantially 35 nickel, substantially 15 chromium, substantially 0.75% carbon, substantially 1.20% silicon, substantially 2.15% columbium, substantially 0.13% nitrogen, substantially 0.04% selenium, balance essentially iron. 1

7. A heat resisting casting consisting essentially of 32% to 38% nickel, 14% to 20% chromium, up to 1.5% carbon, 1% to 2% manganese, 1% to 2% silicon, 1% to 3% columbium, 0.05% to 0.2% nitrogen, .04% to 0.1% selenium, balance essentially iron.

prepared accord- 8. A heat resisting casting consisting essentially of substantially 35% nickel, substantially 15% chromium, up to 1.5% carbon, 1% to 2% manganese, 1% to 2% silicon, 1% to 3% columbium, 0.05% to 0.2% nitrogen, substantially .05 selenium, balance essentially iron.

9. A heat resisting casting consisting essentially of 32% to 38% nickel, 14% to 20% chromium, substantially 0.75% carbon, substantially 1.20% silicon, substantially 2.15% columbium, substantially .13% nitrogen, substantially 0.04% selenium, balance essentially iron.

10. A heat resisting casting consisting essentially of substantially 35% nickel, substantially 15% chromium, substantially 0 75.%'-carbon, substantially 1.20%" silicon, substantially 2.15 columbium; substantially .13 nitrogen, substantially 0.04% selenium, balance essentially iron.

References Cited in the file of this patent UNITED STATES PATENTS German Oct. 8, 1946 Rich Mar. 30, 1948 OTHER REFERENCES 

1. AN ALLOY CONSISTING ESSENTIALLY OF 32% TO 38% NICKEL, 14% TO 20% CHROMIUM, UP TO 1.5% CARBON, 1% TO 2% MANGANESE, 1% TO 2% SILICON, 1% TO 3% COLUMBIUM, 0.05% TO 0.2% NITROGEN, .04% TO 0.1% SELENIUM, BALANCE ESSENTIALLY IRON. 